Enhanced Neel temperature in EuSnP under pressure

We present the combined results of single crystal X-ray diffraction, physical properties characterization, and theoretical assessment of EuSnP under high pressure. Single crystals of EuSnP prepared using Sn self-flux crystallize in the tetragonal NbCrN-type crystal structure (S.G. P4/nmm) at ambient pressure. Previous studies have shown that for Eu ions, seven unpaired electrons impart a 2+ oxidation state. Assuming the oxidation states of Eu to be +2 and P to be -3, each Sn will donate one electron, with one p valence electron left for forming a weak Sn-Sn bond. According to the high-pressure single crystal X-ray diffraction measurements, no structural phase transition was observed up to approximate to 6.2 GPa. Temperature-dependent resistivity measurements up to 2.15 GPa on single crystals indicate that the phase-transition temperature occurring at the Neel temperature (T-N) is significantly enhanced under high pressure. The robust crystallography and enhanced antiferromagnetic transition temperatures can be rationalized by the electronic structure calculations and chemical bonding analysis. The increasing Eu-P bonding interaction is consistent with the lattice parameter changing and enhanced T-N. Moreover, the molecular orbital diagram shows that the weak Sn-Sn bond can be squeezed under pressure, acting as a compression buffer to stabilize the structure.